The present invention relates to a graft copolymer and a composition containing the graft copolymer. Coatings obtained by the use of the graft copolymer or the composition containing the graft copolymer of the present invention can maintain excellent water repellent, oil repellent and stain resistant properties over a long period of time.
In recent years, coatings on outer walls of tall buildings and vehicles, etc. are required to be maintenance-free in view of maintenance of esthetic values, cleaning work saving, and the like.
In such applications, curing type acrylic resins known as acrylurethane resins have been heretofore used. However, durability of their coatings is not so satisfactory, and there are problems such as surface chalking or yellowing. Thus, they are hardly maintenance free due to necessity of frequent peeling and repainting operations.
Organic solvent-soluble fluoro-polymers represented by those described in Japanese Unexamined Patent publications Nos. 1982-34107 and No.1986-57609 may be mentioned as one which can improve durability of coatings, and which are more widely used. Although organic solvent-soluble fluoro-polymers have solved the problems of surface chalking and yellowing and initial stain resistant property, their water repellent and oil repellent properties are not so high. A further problem is that exposure to the outdoors environment unexpectedly deteriorate their water and oil repellent properties with lapse of time, and stain resistant property becomes gradually poor on this account.
A resin which is called as acrylsilicone type resin has recently appeared on the market as one that can impart the desired stain resistant property to such coatings. This resin generally forms hydrophilic coatings, and stains adhered to the surface are washed away by rain water. Although the acrylsilicone type resin shows relatively good performance in terms of the stain resistant property, there is a problem that ice and snow, that adhere to the surface of buildings and vehicles in cold districts due to hydrophilic nature of the surface, are difficult to remove, or they make visibility of traffic signs and advertising boards extremely poor.
In Japanese Unexamined Patent Publication No. 1998-291981, a hydrophobic coating-forming resin that may solve the above-mentioned problem is described. This resin does not suffer from the above-mentioned drawback because the formed surface is hydrophobic, and it shows sufficient stain resistant performance. However, although this resin maintains sufficient performance so long as it is used in an environment where the resin is not exposed to light, such as indoors, it has a problem that its water repellent and oil repellent properties, and hence its stain resistant property, decrease with lapse of time just as the above-mentioned solvent-soluble fluoro-polymer, when it is in an outdoor (light exposed) environment.
Under such circumstances, what is to be attained by the present invention is to provide a graft copolymer from which coatings can be obtained such that the water repellent and oil repellent properties thereof do not drop in outdoor (light exposing) environment for a long period of time and excellent stain resistant property can be maintained. Another object is to provide a coating composition that contains such a graft copolymer.
The above-mentioned object can be attained by a graft copolymer of the present invention comprising a copolymerized product of
(A) from 2 to 66 percent by weight of an organic solvent-soluble fluoro-polymer having, via urethane linkage, radically polymerizable unsaturated bond portion,
(B) from 4 to 40 percent by weight of polysiloxane of which one terminal group is radically polymerizable, said polysiloxane being one represented by the general formula: 
xe2x80x83wherein R1 is a hydrogen atom or a hydrocarbyl group of 1 to 10 carbon atoms; R2, R3, R4, R5 and R6 may be the same or different and are, respectively, a hydrogen atom or a hydrocarbyl group of 1 to 10 carbon atoms, and n is 2 or greater, and/or one represented by the general formula: 
xe2x80x83wherein R7 is hydrogen atom or a hydrocarbyl group of 1 to 10 carbon atoms, R8, R9, R10, R11 , and R12 may be the same or different and are hydrogen atom or a hydrocarbyl group of 1 to 10 carbon atoms, p is an integer of 0 to 10, and q is an integer of 2 or greater,
(C) from 1 to 50 percent by weight of a radically polymerizable monomer having one radically polymerizable double bond and at least one fluoroalkyl group in a molecule, and
(D) from 4 to 93 percent by weight of a radically polymerizable monomer other than components (A), (B) and (C) (this may be hereinafter sometimes referred to simply as non-reactive, radically polymerizable monomer), provided that the sum of the amounts of components (A), (B), (C), and (D), plus impurities, is 100 percent by weight.
The present invention also relates to a composition containing the above-mentioned graft copolymer.
Coatings obtained by applying a composition comprising the above-mentioned graft copolymer have the advantage that water and oil repellent properties do not drop in an outdoor (light exposing) environment for a long period of time, and hence have an excellent stain resistant property.